This invention relates to a method of manufacturing flying magnetic transducer assemblies, and more particularly to such transducer assemblies comprising a thin-film transducer deposited upon a substrate. More specifically, the invention relates to such a transducer which starts and stops in contact with the magnetic medium and is supported above that medium on an air bearing during operation.
Magnetic recording systems utilizing transducer heads flying on an air bearing film over rotating magnetic recording discs are well known in the art. One commonly used type is illustrated and described in some detail in U.S. Pat. No. 3,855,625 to Garnier et al. Such a structure is formed with a pair of spaced apart air bearing rails with a magnetic transducer at the rear of each of such rails. These heads are resiliently loaded toward the surface of the magnetic medium, generally a rotating disc, to a predetermined degree to cause them to fly very close, on the order of 50 microinches, above that surface.
To achieve ever smaller and more precise recording transducers, recent years have seen the development of thin-film transducers which are deposited onto the slider by various photolithographic and etching techniques well known in the semiconductor art. This thin-film transducer replaces the ferrite core transducer which has been used in the past. In conventional manufacturing techniques the thin-film transducer, having a magnetic gap or throat height which is considerably larger than desired, is applied to the substrate material at the rear of the air bearing rails. Then, the slider substrate material is lapped to achieve the desired configuration and dimensions for the air bearing rails. At this same time, the rear portion of the rails is lapped to achieve a desired throat height on the transducer. While this manufacturing technique is relatively straightforward, it has resulted in a very low yield of usable heads. This low yield is due largely to the effects of the abrasive lapping of the rails adjacent the thin-film transducer throat causing delamination and chipping of the transducer throat away from the slider, thus rendering it unusable.
The problem is considerably more complicated than with the conventional magnetic core transducers, since those conventional heads required throat height tolerances on the order of .+-.200 microinches. Thin-film heads desired for higher performance applications may have throat height tolerances ten times tighter, on the order of .+-.20 microinches. With this required accuracy in precision, standard manufacturing techniques have given a yield of nearly zero usable heads.
The manufacturing tolerances for these devices are quite important, since the read and write characteristics of thin-film recording transducers are very much dependent upon throat height. The throat height tolerance limits define the outside limits at which the transducers will read and write acceptably in a high performance disc drive. In other words, a small range of throat heights produces a large range of performance characteristics. Obviously such differences in performance from head to head must be corrected and compensated for in the electronics and other portions of the disc drive system to achieve consistent operation.
One characteristic of thin-film recording transducers is that of improving read and write performance with decreasing throat height. However, due to the difficulty in lapping to a predetermined dimension with microinch tolerances, current manufacturing processes have prevented thin-film heads from realizing their full operational potential. As noted above, current manufacturing techniques dictate lapping the thin-film transducer at the time of lapping the slider to form the air bearing rails with the desired flatness and surface finish. Since this lapping conventionally extends all the way to the rear of the rails, the operation also changes and controls the thin-film transducer throat height. Furthermore, this lapping has tended to delaminate and lift the transducer from the slider, frequently destroying it and reducing the yield of the process.
Another problem currently experienced by these conventional heads, referred to as "taper-flat air bearing heads" is that the thin-film transducer at the rear of the air bearing rail contacts the disc surface whenever the head contacts the disc, since the transducer is contiguous with the end of the air bearing rail. Such contact with the disc surface also causes delamination and lifting of the transducer from the slider, further damaging and compromising the read/write capability of the head.